1. Field of the Invention
The present invention relates to a semiconductor memory device and a driving method of the same.
2. Related Art
Generally, a semiconductor memory device adopts a redundancy function of replacing a defective memory cell by a memory cell in a redundancy region (spare region) prepared in a memory chip in advance to improve yield. The redundancy function is to replace a defective memory cell by a memory cell in the spare region based on address information read from a fuse during a power-on state. This can provide the memory chip as a non-defective product as a whole.
The information necessary to replace the defective memory cell by the memory cell in the spare region is stored in the fuse. The fuse is conventionally provided separately from a memory cell array. Due to this, the memory chip is disadvantageously made large in size.
Furthermore, when a laser fuse is employed as this fuse, it is necessary to add a step of using a laser to write data. This disadvantageously increases manufacturing costs of the memory chip.
Moreover, when the fuse differs in configuration from each memory cell, it is necessary to evaluate reliability of the fuse separately from that of the memory cell. This also disadvantageously increases the manufacturing costs of the memory chip.